加氯消毒过程中纯细菌物质生成消毒副产物研究

按照UFC方法对水体中3种常见细菌Acinetobacter junii、Staphylococcussciuri和Escherichia coli进行纯细菌加氯消毒处理,同时考察水中溴离子对纯细菌物质生成DBPs的影响.结果表明,3种细菌均为DBPs前体物,加氯消毒生成的DBPs除水合三氯乙醛(CHD)外,生成的三卤甲烷(THMs)物质主要为氯仿(TCM),卤乙腈(HANs)物质主要为二氯乙腈(DCAN).氯仿的生成量与细菌物质TOC浓度无明显关系,但HANs和CHD生成量均随细菌TOC浓度增大而增加.其中革兰氏阳性细菌Staphylococcus sciuri生成的DCAN和CHD比革兰氏阴性细菌Acinetobacter junii和Escherichia coli生成的要高,说明细胞壁的化学组分可能是DCAN和CHD生成的影响因素之一.Escherichia coli细菌反应液中溴离子(Br-)存在时,除生成CHD、TCM及DCAN外,THMs和HANs中的溴代种类CHBr3随Br-增多而持续增加,相反TCM持续减少.当Br-浓度为4mg.L-1时,TBM浓度增至最高127.9μg.L-1;HANs和CHD生成量随Br-浓度增加先有所增加,随后持续降低至低于检测限;Br离子存在时THMs为主要DBPs种类.

Disinfection by-product formation by bacterial cell materials during chlorination

Three pure bacterial cultures, Acinetobacter junii, Staphylococcus sciuri and Escherichia coli, representing common bacteria found in drinking water sources, were chlorinated according to the Uniform Formation Conditions (UFC) to evaluate the disinfection by-products (DBPs) formed from their cellular materials during drinking water treatment. The effect of bromide on DBPs formation from cellular materials was also evaluated. The results confirmed that cellular materials were the DBPs precursors during chlorination. Trihalomethanes (THMs), haloacetunitriles (HANs) and chloral hydrate (CHD) formation were detected after chlorination of the three pure bacterial cultures. The major species of THMs and HANs were chloroform (TCM) and dichloroacetenitrile (DCAN), respectively. The concentrations of DCAN and CHD increased with the total organic carbon (TOC) in terms of the concentration of bacterial materials, but such relationship was not found with TCM. Furthermore, the DBPs formation by Staphylococcus sciuri, a gram positive bacterium, was higher than that of the gram negative bacteria, Acinewbacterjunii and Escherichia coli, suggesting that the chemical composition of the bacterial cell wall could be a key factor in DBP formation. In the presence of bromide ions, in addition to the TCM, DCAN and CHD, brominated DBPs were formed, including CHBr_3 (TBM), CHClBr_2 (DBCM) , CHCl_2 Br (BDCM) and CHBr_2 CN (DBAN) , CHBrClCN (BCAN). The amount of TBM formation in chlorinated water increased linearly with the Br- concentration, while the content of TCM continuously decreased. The content of TBM continuously increased with Br~- concentration to a maximum of 127.9 μg·L~(-1) TBM at a Br~- concentration of 4 rag-L-t. However, the brominated species of HANs and CHD increased with the increase of Br - concentration at the lower range only, from 0 mg·L~(-1) to 0.5 rag·L~(-1). The concentrations of these brominated species continuously decreased at higher Br - concentrations, from 0.5 mg·L~(-1) to 4 mg·L~(-1) , until they were lower than the detection limits. THMs were the main DBP species when there was a high concentration of bromide.